Heat exchanger apparatus for producing steam or the like

ABSTRACT

An improved heat exchanger apparatus for producing steam or the like wherein a fluid is heated via a burner assembly as the fluid passes through a coil assembly to an outlet steam nozzle, the coil assembly including an outer helically wound coil and an inner helically wound coil generally disposed within the outer helically wound coil and having one end thereof disposed generally near the burner assembly. The coil layers of the outer coil are separated so that the fluid passing therethrough is maintained at a relatively low temperature level with respect to the fluid passing from the inner coil to facilitate the insulation of the coil assembly and to enhance the heat transfer efficiency of the heat exchanger apparatus.

United States Patent Minton HEAT EXCHANGER APPARATUS FOR PRODUCING STEAM OR THE LIKE [75] Inventor: Richard L. Minton, Norman, Okla.

[73] Assignee: Bantam Steam Company, Norman,

Okla.

[22] Filed: Nov. 13, 1972 [21] Appl. No.: 306,371

[ May 21, 1974 Primary Examiner-Kenneth W. Sprague Attorney, Agent, or Firm-Dunlap, Laney, l-lessin, Dougherty & Codding 5 7] ABSTRACT An improved heat exchanger apparatus for producing steam or the like wherein a fluid is heated via a burner assembly as the fluid passes through a coil assembly to an outlet steam nozzle, the coil assembly including an outer helically wound coil and an inner helically wound coil generally disposed within the outer helically wound coil and having one end thereof disposed generally near the burner assembly. The coil layers of the outer coil are separated so that the fluid passing therethrough is maintained at a relatively low temperature level with respect to the fluid passing from the inner coil to facilitate the insulation of the coil assembly and to enhance the heat transfer efficiency of the heat exchanger apparatus.

9 Claims, 5 Drawing Figures HEAT EXCHANGER APPARATUS FOR PRODUCING STEAM OR THE LIKE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to heat exchangers and, more particularly, but not by way of limitation, to an improved heat exchanger apparatus for producing steam.

2. Brief Description of the Prior Art In the past there have been various devices constructed for heating water to produce steam, the produced steam being utilized in a variety of applications. In some instances, the water has been passed through tubes and the tubes have been disposed in a heated environment, the heat being transferred to the water via the tubes. However, most of these devices have been relatively large, complex and constructed in a manner requiring permanent or fixed installation of the apparatus or a substantial portion thereof.

SUMMARY OF THE INVENTION An object of the invention is to provide an improved heat exchanger apparatus wherein the fluid is heated in a more efficient, faster and more economical manner.

Another object of the invention is to provide an improved heat exchanger apparatus wherein the heated members are insulated in a more efficient and more economical manners.

One other object of the invention is to provide an improved coil assembly for a heat exchanger apparatus which is more efficient and more economical in construction and operation.

Yet another object of the invention is to provide an improved control system for a heat exchanger apparatus.

A still further object of the invention is to provide an improved heat exchanger apparatus for producing steam which can be moved from one location to another in a faster, more efficient and more economical manner.

Another object of the invention is to provide an improved heat exchanger apparatus which is more economical in construction and operation.

Other objects and advantages of the invention will be evident from the following detailed description when read in conjunction with the accompanying drawings which illustrate 'one preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of the heat exchanger apparatus of the present invention.

FIG. 2 is a partial sectional view of the enclosure, the coil assembly and burner assembly of the heat exchanger apparatus of FIG. I, a portion of the inner coil being shown in elevation in FIG. 2.

FIG. 3 is a top plan view of the heat exchanger apparatus of FIG. 1.

FIG. 4 is a bottom plan view of the heat exchanger apparatus of FIG. 1.

FIG. 5 is a partial schematic, partial diagrammatic view of the igniter circuit of the heat exchanger apparatus of FIG. 1.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings in general and to FIG. I through 4 in particular, shown therein and designated by the general reference numeral 10 is a heat exchanger apparatus secured to and supported on a mobile support 12 and constructed in accordance with the present invention. The heat exchanger apparatus 10 is particularly useful for producing steam and operating in the nature of apparatus generally referred to in the art as a steam cleaner" or the like, the heat exchanger apparatus 10 being constructed and supported for transporting to remote locations in a manner to be made more apparent below.

The mobile support 12 basically includes a base frame member 14 and a vertical support structure 16, the vertical support member 16 being connected to the base frame member 14 on one end thereof and having a pair of handles 18 formed on the opposite end thereof.

The mobile support 12 also includes an upper and a lower strap support 20 and 22, respectively, each of the strap supports 20 and 22 being secured about and supportedly connected to an enclosure 24. A pair of wheels 26 are each connected to and journally supported on the base frame 14, the mobile support 12 being constructed to support the various components and assemblies of the heat exchanger apparatus 10 of the present invention in such a manner that the heat exchanger apparatus 10 can be easily transported or wheeled to various remote locations and hooked up to produce steam, in a manner to be described in greater detail below.

The enclosure 24 includes a cylindrically shaped housing 28 comprising a tubular shaped inner member 30, a tubular shaped outer member 32 disposed generally concentrically about the inner member 30, and a layer of heat insulation material 34 disposed and sandwiched generally between the inner and the outer members 30 and 32. In one preferred form, the inner and the outer walls 30 and 32 are each constructed of a galvanized metal and the heat insulation material 34 is constructed of an asbestos like material.

The housing 28 has an upper end portion 36 and a lower end portion 38, the upper strap support 20 extending generally about and being secured to the housing 28 near the upper end 36 thereof and the lower strap support 22 extending generally about and being secured to the housing 28 generally near the lower end 38 thereof. The inner and the outer members 30 and 32 and the heat insulation material 34 of the housing 28 form an opening 40 extending through the housing 28 intersecting the upper and the lower ends 36 and 38 thereof.

A portion of the housing 28, generally near the lower end 38 thereof, is disposed within a portion of a cylindrically shaped wind screen 42. The housing 28 is, more particularly, secured to the wind screen 42 via a plurality of brace members 44, each of the brace members 44 being secured to the lower end portion of the outer member 32 of the housing 28 and to a portion of the inner peripheral surface of the wind screen 42. The diameter of the wind screen 42 is larger than the diameter of the outer member 32 of the housing28 thereby forming a gap 46 between the wind screen 42 and the housing 28 extending circumferentially about the lower end portion of the housing 28. An opening 48 is formed through a portion of the wind screen 42 for accommodating a portion of the heat producing apparatus of the heat exchanger apparatus as will be described in greater detail below.

A plurality of coil supports 50 are disposed within the opening 40 of the housing 28, generally near the lower end 38 thereof. Each of the coil supports 50 is secured to the inner member 30 and includes a flange portion 52 extending a distance generally radially from the inner member 30, as shown more clearly in FIGS. 2 and 4. The flange S2 of each of the coil supports 50 forms an upwardly facing support surface 54, the coil supports 50 being circumferentially spaced about the inner periphery of the housing 28 formed by the opening 40 therethrough and disposed to support a coil assembly 56 in an assembled position during the operation of the heat exchanger apparatus 10. A portion of each of the coil supports 50 also is secured to a portion of the coil assembly 56, in a manner and for reasons to be made more apparent below.

A portion of a gas conduit 58 is disposed through the opening 48 formed in the wind screen 42, one end of the gas conduit 58 being connected to a gas burner 60, as shown more clearly in F 168. 2 and 4. The gas burner 60 is generally centrally disposed and supported within the-opening 40 of the housing 28, generally near the lower end 38 thereof, as shown more clearly in FIG. 2. The gas burner 60 includes a plurality of openings 62 emitting fuel therethrough when the gas conduit 58 is connected to a gas or fuel supply (not shown) for burning within the opening 40 ofthe housing 28 in a manner well-known in the art.

A spark producing device or, more particularly, a spark plug 64 is secured to a portion of the gas burner 60 and disposed generally near the gas outlet openings 62 of the gas burner 60. The spark plug 64' is thus positioned to ignite the gas escaping via the gas outlet openings 62 when the spark plug 64 is activated via an igniter control 66 of the heat exchanger apparatus 10 and the gas burner 60 is connected to the gas supply (not shown) during the starting of the heat exchanger apparatus 10, a spark plug wire 68 being connected on one end to thespark plug 68 and on the opposite end to a portion of the igniter control 66, in a manner and for reasons which will be made more apparent below.

As shown more clearly in FIGS. 1 and 3, a hood 70 is connected and secured to the housing 28, generally near the upper end 36 thereof. More particularly, a plurality of structural braces 72 are connected between the hood 70 and the upper end portion 36 of the housing 28, one end of each structural brace 72 being secured to a portion of the hood 70 and the opposite end of each of the structural braces 72 being secured to a portion of the housing 28.

As shown more clearly in FIG. 2, the coil assembly 56 includes an outer helically wound coil-74 and an inner helically wound coil 76, the inner coil 76 being generally disposed within a portion of the outer coil 74 and being surrounded by a portion of the outer coil 74, as shown in FIG. 2. The outer coil 74 has an upper end portion 80, a lower end portion 82, a fluid inlet end portion 84, a fluid outlet end portion 86 and is wound in a generally helically shaped path generally from the fluid inlet end. portion 84 toward the fluid outlet end portion 86 at a predetermined average mean radius 88.

The inner coil 76 has an upper end portion 92, a lower end portion 94, a fluid inlet end portion 96, a fluid outlet end portion 98 and is wound in a generally helically shaped path generally from the fluid inlet end portion 96 toward the fluid outlet end portion 98 at a predetermined average mean radius 100 generally less or smaller than the average mean radius 88 of the outer coil 74, the outer coil 74 being generally disposed about the inner coil 76.

The coil assembly 56 has a fluid inlet portion 102 and a fluid outlet portion 104, the fluid inlet end portion 84 of the outer coil 74 forming the coil assembly 56 fluid inlet end portion 102. The fluid outlet end portion 86 of the outer coil 74 is connected to the fluid inlet end portion 96 of the inner coil 76 via a coupling 106. The fluid outlet end portion 104 of the inner coil 76 includes a portion 108 formed at a right angle and extending upwardly generally from the lower end portion 94 toward the upper end portion 92 of the inner coil 76 terminating with one end of the inner coil 76 forming the fluid outlet portion 104 of the coil assembly 56, as shown in FIG. 2. I

The fluid inlet end portion 84 of the outer coil 74 is disposed generally near the lower end portion 38 of the housing 28 and generally near the lower end portion 80 of the outer coil 74, the fluid inlet end portion 84 being connected to a fluid conduit 110 via a coupling 112. The fluid outlet end portion 98 of'the inner coil 76 is connected to a fluid conduit 114 via a coupling 116 generally near the upper end portion 92 of the inner coil 76. Thus, the inner coil 76 is coupled to the outer coil 74 and to the conduit 114 via couplings 106 and 116, respectively, and each of the couplings 106 and 116 are each located generally near the upper end portion 36 of the housing 28 so that the inner coil 76 can be disconnected from the outer coil 74 and the conduit 114 via the opening formed in the upper end portion 36 of the housing 28 and removed therefrom for quick, efficient and easy replacement and repair thereof.

The outer coil 74 is wound in a generally upwardly direction such that each of the 360 degree windings of the outer coil 74 forms a coil layer 118 (only thre'e'of the coil layers 118 being designated by reference numerals in FIG. 2 for the purpose of clarity of description). Each of the coil layers 118 of the outer coil 74 is separated by a distance, the separation of the adjacent coil layers 118 increasing generally from the fluid inlet end portion 84 toward the fluid outlet end portion 86 (the separation between two adjacent coil layers 118 being shown in FIG. 2 and designated by the reference numeral 119 for the purpose of clarity of description). More particularly, the coil layers 118 generally near the lower end 82 of the outer coil 74 are separated by a minimum distance and virtually stacked one on top of the other, and the distance or separation between the adjacent coil layers 118 generally near the upper end 80 is increased toward the fluid outlet end portion 86 of the outer coil 74.

The fluid entering the fluid inlet end portion 84 of the outer coil 72 is relatively cool or, in other words, has

of the outer coil 74 disposed generally near the enclosure 24 or, more particularly, near the housing 28 and generally near the fluid outlet end portion 86 of the outer coil 74 with respect to the heated coil surface area of the outer coil 74 disposed generally near the enclosure 24 and generally near the fluid inlet end portion 84 of the outer coil 74, thereby reducing the average temperature level of the fluid within the outer coil 74 and enhancing the insulation efficiency and effectiveness of the heat exchange apparatus 10. In this manner, the average temperature of the outer surface of the housing 28 is maintained at a reduced temperature level during the operation of the heat exchange apparatus 10.

The inner coil 76 is wound in a generally downwardly direction such that each of the 360 windings of the inner coil 76 forms a coil layer 120 (only three of the coil layers 120 being designated by a reference numeral in FIG. 2 for the purpose of clarity of description). Each of the coil layers 120 is separated by a minimum distance or separation and, in a preferred form, each of the coil layers 120 are stacked one on top ofanother generally from the upper end 92 to the lower end 94 of the inner coil 76, thereby providing the maximum coil surface area between the upper and the lower ends 92 and 94 of the inner cell 76 for reasons which will be made more apparent below.

The lower end 94 of the inner coil 76 is disposed generally above the gas burner 60 and, more particularly, is disposed above the gas burner 60 and positioned such that the lower end 94 of the inner coil 76 is disposed at approximately the tip or hottest point of the flame from the gas burner 60. The overall length of the inner coil 76 between the upper end portion 92 and the lower end portion 94 is relatively smaller than the overall length of the outer coil 74 generally between the upper end portion 80 and the lower end portion 82 thereof, as shown in FIG. 2. In other words, the lower end portion 94 of the inner coil 76 is disposed above the gas burner 56 and positioned approximately within the hottest portion of the gas burner 60 flame, for reasons which will be made more apparent below.

The heat exchanger apparatus includes a fluid pump 122 having an inlet (not shown) connected to a fluid inlet conduit 124, the fluid inlet conduit 124 being connected to a fluid supply (not shown). The outlet of the fluid pump 122 is connected to the fluid inlet conduit 110, the fluid pump 122 pumping fluid from the fluid reservoir (not shown) through the fluid inlet conduit 124 and through the inner and the outer coils 74 and 76 to a nozzle 126 connected to the end of the fluid conduit 114 in a driven position of the fluid pump 122.

As shown in FIGS. 1, 2 and 3, the fluid pump 122 is drivingly connected to a pump drive 128 or, more particularly, to an electric motor 128, the electric motor 128 being connected to an electrical power supply via an on-off switch 130 supported in a control box 132 of the heat exchanger apparatus 10. The on-off switch 130 is thus interposed between the electric motor or pump drive 128 and the electrical power supply for activating the pump drive 128 to drive the fluid pump 122 coupled thereto, the utilization and the various interconnections of an on-off switch such as the on-off switch 130 being well-known in the art.

The end of the gas conduit 58, opposite the end thereof connected to the gas burner 60, is connected to a gas supply (not shown) via a conduit 134, a gas solenoid valve 136 being interposed between the gas conduit 58 and the conduit 134. The gas solenoid valve 136 is thus interposed in the gas inlet conduits 58 and 134 and positioned to interrupt the flow of gas therethrough in a de-energized position of the gas solenoid valve 136, the gas solenoid valve 136 being positioned in an opened position allowing the flow of fuel or gas therethrough in an energized position thereof, in a manner to be described in greater detail below.

A thermal cut-off switch 138 is interposed in the conduit 114, generally between the coil assembly 56 and the nozzle 126, as shown in FIG. 1. The switch 138 is constructed to sense the temperature level of the fluid in the conduit 114 and is electrically connected to the gas solenoid valve 136 to automatically de-energize the gas solenoid valve 136 when the sensed temperature level of fluid exceeds a preset or predetermined high temperature level. Thermal cut-off switches and gas solenoid valves constructed to operatein a manner similar to that described before with respect to the switch 138 and the valve 136 are well-known in the art and commercially available.

The igniter control 66 of the heat exchanger apparatus 10 includes a push-button type of momentary switch 140 supported in the control box 132, as shown in FIGS. 1 and 3. The push-button switch 140 is interposed between the electrical power supply and the gas solenoid valve 136 and between the electrical power supply and an igniter control circuit 142, the pushbutton switch 140 being connected to the gas solenoid valve 136 and energizing the gas solenoid valve 136 in a depressed position thereof. The push-button switch 140 is thus connected to the gas solenoid valve 136 and to the igniter control circuit 142 such that, in a depressed position of the switch 140, electrical continuity is simultaneously established between the electrical power source and the igniter control circuit 150 and between the electrical power source and the gas solenoid valve 136 for simultaneous activation and energization during the operation of the heat exchanger apparatus 10, thereby simultaneously positioning the gas solenoid valve 136 in the open position with the activation of the igniter control circuit 142. The igniter control circuit 142, shown schematically in FIG. 5, is connected to the electrical power supply (diagrammat ically shown in FIG. 5 as a AC power supply) via a pair of conductors 152 and 154. The push-button switch is interposed in the conductor 152 connecting the igniter control circuit 142 to the electrical power supply in a depressed position thereof.

The igniter control circuit is generally interposed between the electrical power supply and the spark plug 64, the igniter control circuit being constructed to connect the spark plug 64 to the electrical power supply energizing the spark plug 64 and causing a spark generally over the gas outlet openings 62 of the gas burner 60 thereby igniting the gas burner 60 flame. A silicon controlled rectifier 156 is connected between the conductors 152 and 154, the anode of the silicon controlled rectifier 156 being connected to the conductor 152 at a junction 158 and the cathode of the silicon controlled rectifier 156 being connected to the conductor 154 at a junction 160, as schematically shown in FIG. 5. A resistor 162 and a diode 164 are connected in series and interposed in the conductor 152, generally between the electrical power supply and the junction side of a transformer 166.

The gate of the silicon controlled rectifier 156 is connected to 'a neon indicator lamp 168 via a conductor 170. A first capacitor-resistor network 172 and a second capacitor-resistor network 174 are each connected to the gate of the silicon controlled rectifier 156 and the transformer 166. The first capacitor-resistor network 172 comprises a resistor 176 and a capacitor 178, and the second capacitor-resistor network 174 comprises a resistor 180 and a capacitor 182, the resistor 176 connected to the conductor 170 generally between the silicon controlled rectifier 156 and the neon indicator lamp 168 and connected to the conductor 154 generally between the junction 160 and the transformer 166.

The primary side of the transformer 166 is connected to the junction 158, as mentioned before, and also to a junction 184. The capacitor 182 is connected to the junction 184 and to the junction 160, as shown in FIG. 5. The resistor 180 is connected to the junction 184 and to the neon indicator lamp 168. The capacitor 178 is connected generally between the neon indicator lamp 168 and the resistor 180, the opposite end of the capacitor 178 being connected generally between the capacitor 182 and the resistor 176 connection to the junction 160. The secondary coil of the transformer 166 is connected to ground on one side thereof via a conductor 186, the opposite side of the secondary coil of the transformer 166 being connected to the spark plug 64 via the spark plug wire 68, schematically shown in FIG. and mentioned before.

In the depressed position of the push-button switch 140, the gas solenoid valve 136 is energized allowing gas to flow to the gas burner 60 and through the openings 62 thereof and the igniter control circuit 142 is activated to connect a relatively high voltage to the spark plug 64 via the transformer 166 producing a spark generally above the gas burner 60 and igniting the gas burner 60 flame. The resistor 162 limits the amount of current passing through the silicon controlled rectifier 156 during thatportion ofthe operation of the heat exchanger apparatus 10 when the silicon controlled rectifier 156 is in the conducting position thereof, the resistor 162 also limiting the amount of current drawn from the electricalpower supply in the event of a malfunction in the igniter control circuit 142.

The 'diode 164 is positioned in the conductor 152 between the electrical power supply and the capacitor 178 such that the capacitor 178 is charged in a conducting position of the silicon controlled rectifier 156 during that portion of the alternating-current cycle when the polarity of the conductor 152 is positive with respect to the polarity of the conductor 154, the silicon controlled rectifier 156 being a uni-directional device with respect to the conducting of current therethrough or, in other words, the silicon controlled rectifier 156 conducting current only when the anode thereof is positive in polarity with respect to the cathode thereof.

The energy stored in the capacitor 182 is charged through the resistor 162, the diode 164 and the primary capacitor 178. The resistor 180 determines the rate at which the capacitor 182 is charged. The resulting potential difference across the resistor 176 is applied to the gate terminal of the silicon controlled rectifier 156 and triggers the silicon controlled rectifier 156 into a conducting position. In the conducting position of the silicon controlled rectifier 156, the capacitor 182 is discharged via the primary side of the transformer 166 and the silicon controlled rectifier 156. The discharging of the capacitor 182 and the resulting current flow through the transformer 166 induces a high voltage across the secondary side of the transformer 166, this voltage being connected to the spark plug 64 and resulting in the ignition of the spark to ignite the gas being discharged via the gasburner 60.

When the capacitor 182 is discharged, the silicon controlled rectifier 156 is biased in a non-conducting position. The ignition cycle resulting in the spark being created via the spark plug 64 is repeated via the igniter control circuit 142 to assure that the gas being discharged via the gas burner 60 is ignited in'the event the flame created thereby should go out for some reason during the operation of the heat exchanger apparatus 10.

OPERATlON OF THE PREFERRED EMBODIMENT The heat exchanger apparatus 10, described in detail before, is constructed to provide a portable, compact unit for producing steam or the like in a more efficient and more economical manner. After the heat exchanger 10 has been positioned at a desired, remote location, the fluid inlet conductor 124 is connected to a fluid source (not shown) such as an ordinary water outlet or the like, for example. The gas supply conduit 134 is then connected to the gas source (not shown) such as a portable low-pressure gas (L.P.G.) container or the like, for example, a regulator (not shown) being connected to the gas source to vary the amount of gas passing to the gas burner 60 during the operation of the heat exchanger 10 and thus varying the temperature of the fluid existing at the nozzle 126, the gas source and regulator being well-known in-the art and commercially available.

The on-off switch is then switched to the on position connecting the electrical power source to the pump drive 128 activating the pump drive 128 to drive the fluid pump 122 coupled thereto, thereby pumping the fluid from the fluid source (not shown) to the coil assembly 56 via the fluid conduits 124 and 110. The gas solenoid valve 136 is activated simultaneously with the activation of the igniter control circuit 142, thereby opening the gas solenoid valve 136 allowing gas from the gas source (not shown) to be connected to the gas burner 60 via the gas conduits 134 and S8. The gas solenoid valve 136 and the igniter control circuit 66 are each connected to and activated simultaneously via the depression of the push-button switch 140, as described before.

The water or fluid entering the fluid inlet end portion 86 of the outer coil 74 from the fluid pump 122 has a substantially lower temperature level with respect to the temperature level of the fluid passing through the fluid outlet end portion 98 of the inner coil 76 in an operating position of the heat exchanger apparatus 10, the fluid from the fluid pump 122 being pumped through the outer coil 74 and moving in a generally upwardly direction from the lower end portion 82 toward the upper end portion 80 thereof. As the fluid moves through the outer coil 74, the fluid is heated via the gas burner 60 flame and thus the temperature level of the fluid in the outer coil 74 generally increases as the fluid moves through the outer coil 74 in a direction generally from the lower end 82 thereof toward the upper end 80 thereof, the fluid leaving the fluid outlet end portion 86 of the outer coil 74 being of a relatively higher temperature level with respect to the fluid entering the fluid inlet end portion 84 of the outer coil 74 as a result of the heat exchange between the gas burner 60 flame and the fluid via the fluid conduits forming the outer helically wound coil 74. The distance or separation between each of the coil layers 118 of the outer coil 72 is increased toward the upper end 80 of the outer coil 74, as mentioned before, to control the average maximum temperature level of the fluid within the outer coil 74, thereby controlling the average temperature level of the fluid in the outer coil 74 generally near the housing 28. In this manner the average temperature level of the fluid in the outer coil 74 is controlled with respect to the housing 28 to cooperate with the heat insulation material 34 to maintain the average temperature level of the housing 28 along the outer periphery thereof formed by the tubular shaped outer member 32 at a safe, relatively low temperature level.

The heated fluid is moved from the outer coil 74 through the inner coil 76 via the coupling 106 connection therebetween. The fluid then moves through the inner coil76 generally from the fluid inlet end portion 96 thereof in a generally downwardly direction from the upper end portion 92 toward the lower end portion 94 of the inner coil 76. The distance or separation between the coil layers 120 of the inner coil 76 is maintained at a minimum so that the maximum coil area is disposed generally between the upper end 92 and the lower end 94 of the inner coil 76, thereby exposing a maximum coil area of the inner coil 76 to the gas burner 60 flame. The lower end 94 of the inner coil76 is disposed generally above the gas burner 60 and positioned generally within the hottest portion of the gas burner 60 flame, thereby assuring a maximum heat transfer between the gas burner 60 flame and the fluid flowing through the inner coil 76 prior to the fluid being moved through the upwardly extending portion 108 of the inner coil 76 and being coupled to the fluid outlet conduit 114 via the coupling 116.

The temperature level of the fluid is thus elevated while passing through the outer coil 74 and is further elevated while passing through the inner coil 76, the temperature level of the fluid being raised to a superheated region within the inner coil 76 for connection to the steam producing outlet nozzle 126. The gas burner 60 flame and the coil assembly 56 are each constructed so that the fluid passing from the coil assembly 56 to the nozzle 126 is heated to a sufficient temperature level to produce steam at the nozzle 126 in an open position thereof. The thermal cut-off switch 138 located in the conduit 114 senses the temperature level of the fluid generally at the nozzle 126 and de-energizes and closes the gas solenoid valve 136 when the sensed temperature level exceeds a predetermined, preset maximum temperature level.

in one operational embodiment, the thermal cut-off switch 138 was preset to de-energize the gas solenoid valve 136 when the fluid reaches a sensed temperature level exceeding 350 F., for example. In this particular embodiment, the pressure level of the fluid within the coil assembly 56 was maintained between p.s.i. and p.s.i., and the maximum pressure level of the gas at the gas burner 60 was approximately 4.5. p.s.i., the gas pressure level at the gas burner 60 being set at approximately one-tenth p.s.i. during the igniting of the gas burner 60 flame and increased to approximately 3.0 p.s.i. to 4.0 p.s.i. during the operation of the heat exchanger apparatus 10. Further, a one-half horsepower electric motor was utilized to drive the pump 122.

Changes may be made in the construction and the operation of the various components and assemblies of the heat exchanger apparatus 10 disclosed herein without departing from the spirit and the scope of the in vention as defined in the following claims.

What is claimed is: I

1. Heat exchanger apparatus for heating a fluid flowing through a portion thereof, comprising:

enclosure means having an opening formed in a portion thereof;

heat producing means having a portion supported near a portion of the openingin the enclosure means; and

a coil assembly receiving the fluid at a fluid inlet portion thereof and discharging the fluid at a fluid outlet portion thereof, comprising:

a generally helically wound outer coil disposed generally within a portion of the enclosure means opening, having a fluid inlet end portion and a fluid outlet end portion, the fluid inlet end portion forming the coil assembly fluid inlet end portion; and

a generally helically wound inner coil disposed generally within a portion of the enclosure means opening, having a fluid inlet end portion and a fluid outlet end portion, the fluid inlet end portion connected to the fluid outlet end portion of the outer coil and the inner coil fluid outlet end portion forming the coil assembly fluid outlet end portion, a portion of the inner coil generally near the fluid outlet end portion thereof disposed generally near the heat producing means, the outer coil winding from the fluid inlet end portiontoward the fluid outlet end portion thereof at a predetermined mean radius, the inner coil winding from the fluid inlet end portion toward the fluid outlet end portion thereof at a predetermined mean radius smaller than the mean radius of the outer coil, the outer coil disposed generally about the inner coil and generally near the enclosure means, and the separation between adjacent coil layers of the outer coil increasing generally near the fluid outlet end portion thereof reducing the heated outer coil surface area disposed generally near the fluid outlet end portion of the outer coil relative to th'e outer coil surface area disposed generally near the fluid inlet portion of the outer coil.

2. The apparatus of claim 1 wherein the heat producing means includes: a gas burner; gas solenoid valve means connecting the gas burner to a gas supply in an energized position thereof; igniter means igniting the gas at the gas burner in an activated position thereof; and push-button switch means connected to the gas solenoid valve means and to the igniter means simultaneously energizing the gas solenoid valve means and energizing the igniter means in a depressed position thereof.

3. The apparatus of claim 2 defined further to include: pump means connected to the fluid inlet end portion of the coil assembly receiving fluid and pumping fluid through the coil assembly in a driven position thereof; pump drive means driving the pump means in an activated position thereof; and on-off switch means connected to the pump drive means activating the pump drive means in an on position thereof.

4. The apparatus of claim 2 wherein the igniter means is defined further to include:

spark plug means disposed near the gas burner means producing a spark igniting the gas burner means in an energized position thereof; electrical power supply means connected to the spark plug means energizing the spark plug means when connected thereto; and 1 igniter control circuit means interposed between the spark plug means and the electrical power supply means connecting a high voltage and activating the spark plug means in one position thereof.

5. The apparatus of claim 4 wherein the igniter control means includes:

transformer means connected to spark plug means and the electrical power supply means;

silicon controlled rectifier means connected between the transformer means and the electrical power supply means conducting in one position thereof;

first capacitor-resistor means connected to the gate of the silicon controlled rectifier means triggering the silicon controlled rectifier in a conducting position at a predetermined potential level of the capacitor-resistor means; and

second capacitor-resistor means connected to the transformer means and to the electrical power supply means and being charged in a connected position thereof to the electrical power supply means and charging the first capacitor-resistor means to the predetermined potential level positioning the silicon controlled rectifier means in the conducting position, the second capacitor-resistor means being discharged in the conducting position of the silicon controlled rectifier means inducing a voltage across the transformer means activating the spark plug means.

6. The apparatus of claim 5 wherein the igniter control means includes: diode means interposed between the electrical power supply means and the first and the second capacitor-resistor means for charging the second capacitor-resistor means therethrough in a forward biased position thereof.

7. The apparatus of claim 1 defined further to include:

mobile support means supporting the enclosure means, the heat producing means and the coil assembly for transportation to remote locations.

8. Heat exchanger apparatus for heating a fluid, comprising: 4

a generally tubular shaped inner member having an opening formed in a portion thereof and having an upper end portion and a lower end portion;

a generally tubular shaped outer member disposed generally concentrically about the inner member;

heat producing means having a portion supported near a portion of the opening of the inner member for producing heat in the opening; and

a coil assembly receiving the fluid at a fluid inlet portion thereof and discharging the fluid at a fluid out- 7 let portion thereof, comprising:

a generally helically wound outer coil having coil layers disposed within the inner member opening and having a fluid inlet end and a fluid outlet end, the fluid inlet end connected to the fluid inlet portion of the coil assembly; and i a generally helically wound inner coil having coil layers disposed within the outer coil and having a fluid inlet end and a fluid outlet end, the fluid inlet end connected to the outer coil fluid outlet end and the fluid inlet end connected to the fluid outlet portion of the coil assembly, the length of the inner coil being smaller than the length of the outer coil, and the separation between adjacent coil layers of the outer coil increasing generally near the fluid outlet end thereof.

9. The apparatus of claim 8 wherein there is heat insulation material disposed and sandwiched generally between the inner and the outer members. 

1. Heat exchanger apparatus for heating a fluid flowing through a portion thereof, comprising: enclosure means having an opening formed in a portion thereof; heat producing means having a portion supported near a portion of the opening in the enclosure means; and a coil assembly receiving the fluid at a fluid inlet portion thereof and discharging the fluid at a fluid outlet portion thereof, comprising: a generally helically wound outer coil disposed generally within a portion of the enclosure means opening, having a fluid inlet end portion and a fluid outlet end portion, the fluid inlet end portion forming the coil assembly fluid inlet end portion; and a generally helically wound inner coil disposed generally within a portion of the enclosure means opening, having a fluid inlet end portion and a fluid outlet end portion, the fluid inlet end portion connected to the fluid outlet end portion of the outer coil and the inner coil fluid outlet end portion forming the coil assembly fluid outlet end portion, a portion of the inner coil generally near the fluid outlet end portion thereof disposed generally near the heat producing means, the outer coil winding from the fluid inlet end portion toward the fluid outlet end portion thereof at a predetermined mean radius, the inner coil winding from the fluid inlet end portion toward the fluid outlet end portion thereof at a predetermined mean radius smaller than the mean radius of the outer coil, the outer coil disposed generally about the inner coil and generally near the enclosure means, and the separation between adjacent coil layers of the outer coil increasing generally near the fluid outlet end portion thereof reducing the heated outer coil surface area disposed generally near the fluid outlet end portion of the outer coil relative to the outer coil surface area disposed generally near the fluid inlet portion of the outer coil.
 2. The apparatus of claim 1 wherein the heat producing means includes: a gas burner; gas solenoid valve means connecting the gas burner to a gas supply in an energized position thereof; igniter means igniting the gas at the gas burner in an activated position thereof; and push-button switch means connected to the gas solenoid valve means and to the igniter means simultaneously energizing the gas solenoid valve means and energizing the igniter means in a depressed position thereof.
 3. The apparatus of claim 2 defined further to include: pump means connected to the fluid inlet end portion of the coil assembly receiving fluid and pumping fluid through the coil assembly in a driven position thereof; pump drive means driving the pump means in an activated position thereof; and on-off switch means connected to the pump drive means activating the pump drive means in an on position thereof.
 4. The apparatus of claim 2 wherein the igniter means is defined further to include: spark plug means disposed near the gas burner means producing a spark igniting the gas burner means in an energized position thereof; electrical power supply means connected to the spark plug means energizing the spark plug means when connected thereto; and igniter control circuit means interposed between the spark plug means and the electrical power supply means connecting a high voltage and activatiNg the spark plug means in one position thereof.
 5. The apparatus of claim 4 wherein the igniter control means includes: transformer means connected to spark plug means and the electrical power supply means; silicon controlled rectifier means connected between the transformer means and the electrical power supply means conducting in one position thereof; first capacitor-resistor means connected to the gate of the silicon controlled rectifier means triggering the silicon controlled rectifier in a conducting position at a predetermined potential level of the capacitor-resistor means; and second capacitor-resistor means connected to the transformer means and to the electrical power supply means and being charged in a connected position thereof to the electrical power supply means and charging the first capacitor-resistor means to the predetermined potential level positioning the silicon controlled rectifier means in the conducting position, the second capacitor-resistor means being discharged in the conducting position of the silicon controlled rectifier means inducing a voltage across the transformer means activating the spark plug means.
 6. The apparatus of claim 5 wherein the igniter control means includes: diode means interposed between the electrical power supply means and the first and the second capacitor-resistor means for charging the second capacitor-resistor means therethrough in a forward biased position thereof.
 7. The apparatus of claim 1 defined further to include: mobile support means supporting the enclosure means, the heat producing means and the coil assembly for transportation to remote locations.
 8. Heat exchanger apparatus for heating a fluid, comprising: a generally tubular shaped inner member having an opening formed in a portion thereof and having an upper end portion and a lower end portion; a generally tubular shaped outer member disposed generally concentrically about the inner member; heat producing means having a portion supported near a portion of the opening of the inner member for producing heat in the opening; and a coil assembly receiving the fluid at a fluid inlet portion thereof and discharging the fluid at a fluid outlet portion thereof, comprising: a generally helically wound outer coil having coil layers disposed within the inner member opening and having a fluid inlet end and a fluid outlet end, the fluid inlet end connected to the fluid inlet portion of the coil assembly; and a generally helically wound inner coil having coil layers disposed within the outer coil and having a fluid inlet end and a fluid outlet end, the fluid inlet end connected to the outer coil fluid outlet end and the fluid inlet end connected to the fluid outlet portion of the coil assembly, the length of the inner coil being smaller than the length of the outer coil, and the separation between adjacent coil layers of the outer coil increasing generally near the fluid outlet end thereof.
 9. The apparatus of claim 8 wherein there is heat insulation material disposed and sandwiched generally between the inner and the outer members. 